1. Field of the Invention
The present invention relates to an on-board current control device controlling an inductive load such as an electromagnetic powder clutch, an electromagnetic valve controlling an oil pressure, and so on, which are equipped in a vehicle.
In particular, the present invention relates to improvement of controllability and productivity of the on-board current control device.
2. Discussion of Background
FIG. 6 is a circuit diagram illustrating a structure of a conventional on-board current control device, for example, disclosed in Japanese Patent No. 2737449. FIG. 7 is a chart illustrating a waveform for explaining an operation of the conventional on-board current control device. In FIG. 6, numerical reference 1 designates a processing unit including a microcomputer and so on, inputting engine control information SE and driving control formation SD, and making a PWM modulator 1a output a current basic pulse width modulating signal S1. Numerical reference 10 designates a D/A converter including a buffer amplifier 11 for a digital signal, a smoothing filter 14 having a resistance 12 and a capacitor 13, and an analog buffer amplifier 15, wherein the current basic pulse width modulating signal S1 is inputted in the butter amplifier 11 for digital signals in the D/A converter 10 so that a waveform thereof is modified. A high frequency component of the signal is removed by the smoothing filter 14. Thus obtained signal is applied to an input terminal (+) of the analog buffer amplifier 15, and a current command signal Is is outputted from an output terminal of the analog buffer amplifier 15.
Numerical reference 21 designates a comparator outputting an on/off signal to a transistor in a later stage from a deviation between the current command signal Is and a current feed-back signal IF, to be inputted as described below. Numerical reference 22 designates a resistance connecting the comparator 21 to a power source. Numerical reference 23 designates a transistor for converting signals. Numerical reference 24 designates an output transistor. A base of the transistor 23, converting signals, receives the on/off signal from the comparator 21 through series resistances 25 and a resistance 26 connected to an earth. A collector of the transistor 23 is connected to a base of the output transistor 24 through a resistance 27, and an emitter of the transistor 23 is grounded. The base of the output transistor 24 is connected to a power source through a resistance 28, and an emitter of the output transistor 24 is connected to the power source. The on/off signal from the comparator 21 makes the signal-converting transistor 23 turn on or turn off, whereby the output transistor 24 is turned on or turned off along with the turning-on and turning-off of the signal converting transistor 23.
A collector of the output transistor 24 is connected to the earth through a circulating diode 31 and simultaneously connected to an output terminal 32. An exciting coil 35 of an electromagnetic clutch 34, as a load, is connected between the output terminal 32 and another output terminal 33 through slip rings 36 and 37. A load current Ic is applied to the exciting coil 35 depending on the turning-on and the turning-off of the output transistor 24 and a turning-on of a quick-break transistor 41, to be described below, whereby a current value of the load current Ic is controlled by the output transistor 24.
A collector of the quick-break transistor 41 is connected to the output terminal 33. A constant-voltage diode 42 is connected between the collector and a base of the quick-break transistor 41, and an emitter of the constant-voltage diode 42 is grounded through a current detecting resistance 43. Both ends of the current detecting resistance 43 are respectively connected to an input terminal (+) and an input terminal (xe2x88x92) of a current detecting amplifier 46 respectively through a resistance 44 and a parallel circuit having a resistance 45 and an adjusting resistance 45a. Further, a feedback resistance 47 is connected between the input terminal (xe2x88x92) of the current detecting amplifier 46 and an output terminal of the current detecting amplifier 46. The current detecting amplifier 46 outputs and supplies the current feedback signal IF, corresponding to the load current Ic, to an input terminal (xe2x88x92) of the above-mentioned comparator 21.
Numerical references 51 and 52 designate signal converting transistors for turning on and turning off the quick-break transistor 41 depending on the signal from the processing unit 1. A base of the signal converting transistor 51 receives a signal from the processing unit 1 through series resistances 53 and a resistance 54 connected to the earth, a collector of the signal converting transistor 51 is connected to a power source through resistances 55 and 56. A base of the signal converting transistor 52 is connected to a connecting point between the resistances 55 and 56, an emitter of the signal converting transistor 52 is connected to the power source, and a collector of the signal converting transistor 52 is connected to the base of the quick-break transistor through a resistance 57. When the signal from the processing unit 1 is a positive potential, the signal converting transistors 51 and 52 are turned on, and the quick-break transistor 41 is turned on; and when the signal is changed to 0, the signal converting transistors 51 and 52 are turned off, and the quick-break transistor 41 is turned off.
In thus constructed conventional on-board current control device, when the engine control information SE and the driving control information SD are inputted into the processing unit 1, the processing unit 1 operates a current command value from the two types of the information SE and SD, modulates the current command value to obtain a PWM modulating signal, and outputs the current basic pulse width modulating signal S1. This current basic pulse width modulating signal S1 is a rectangular wave signal having a weight of modulation in proportional to the current command value illustrated in FIG. 7a. However, because a voltage value is not an ideal waveform, being in a range of 0 through V5 of a voltage of the power source, because of a voltage drop inside a circuit. Therefore, the current basic pulse width modulating signal is converted to a pulse width modulating signal S2 having an ideal waveform illustrated in FIG. 5b by the buffer amplifier 11 for digital signals.
A high frequency component of the pulse width modulating signal S2 is removed by the smoothing filter 14 to be converted to a signal like a direct current. Thereafter, the pulse width modulating signal S2 is applied to the analog buffer amplifier 15. The analog buffer amplifier 15 outputs the current command signal Is illustrated in FIG. 7c and applies to the terminal (+) of the comparator 21. Since the current feed-back signal Is is applied from the current detecting amplifier 46 to the terminal (xe2x88x92) of the comparator 21, the current command signal Is and the current feed-back signal IF are compared. Depending on a difference between these, a signal subjected to the pulse width modulation is outputted from the output terminal of the comparator 21 in response to the difference, the signal converting transistor 23 and the output transistor 24 are turned on or turned off in response to a rate of modulation of the signal to control a current value of the load current Ic, passing through an exciting coil 35 of the electromagnetic clutch 34.
Further, when the electromagnetic clutch 34 is actuated, the signal applied from the processing unit 1 to the signal converting transistor 51 as a positive tension. Therefore, the signal converting transistors 51 and 52 are turned on, and accordingly the quick-break transistor 41 is also turned on. The load current Ic controlled by the output transistor 24 is applied to the exciting coil 35 of the electromagnetic clutch 34. the load current Ic flows through the current detecting resistance 43 to cause a potential difference on both ends of the resistance in proportion to the current value. The potential difference is applied to the current detecting amplifier 46 through the resistance 44 and the parallel circuit of the resistance 45 and the adjusting resistance 45a. The current feed-back signal IF, determined by resistance values of the feed-back resistance 47, the resistance 44, and the parallel circuit of the resistance 45 and the adjusting resistance 45a, is outputted to the comparator 21.
As described, the current Ic controlled by the current command value is applied to the exciting coil 35 of the electromagnetic clutch 34 so as to be actuated. Further, by changing the signal applied from the processing unit 1 to the signal converting transistor 51 to 0, the signal converting transistors 51 and 52 and the quick-break transistor 41 are turned off, whereby the current flowing through the exciting coil 35 is shut off, and the electromagnetic clutch 34 is released to finish an operation.
In the conventional on-board current control device, the current Ic flowing through the exciting coil 35 of the electromagnetic clutch 34 is controlled by the modulating factor of the pulse width modulating signal outputted from the comparator 21, the modulating factor is determined by the current command signal Is and the current feed-back signal IF, and the current feed-back signal IF is determined by resistance values of the feed-back resistance 47, the resistance 44, and the resistance 45. However, there are dispersions in resistance values of the resistances, and there is a dispersion of characteristics in the current detecting amplifier 46. Therefore it is necessary to absorb the dispersions of the components and adjust an amplification factor of the current detecting amplifier 46. Such an operation of adjusting the amplification prevents a flow of a production process, and spoils improvement of a production efficiency, whereby an adjustment using stepwise resistance values of the adjusting resistance 45a results in a stepwise adjustment of the load current Ic, and there are a certain limit in controllability.
It is an object of the present invention to solve the above-mentioned problems inherent in the conventional technique and to provide an on-board current control device facilitating an adjusting operation of adjusting a current supplied to a load, enhancing a production efficiency by abolishing adjusting resistances, and improving a controllability.
According to a first aspect of the present invention, there is provided an on board current control device comprising:
a processing unit outputting a current basic pulse width modulating signal by operating a current command value from engine controlling information and driving control information and outputting a current adjusting pulse width modulating signal from current adjusting information;
a current regulator modulating the current basic pulse width modulating signal by the current adjusting pulse width modulating signal and generating a current command pulse width modulating signal;
a smoothing filter removing a high frequency part of the current command pulse width modulating signal and converting to a current command signal;
a comparator outputting a signal in response to a deviation obtained as a result of a comparison between the current command signal and a current feed-back signal;
an output transistor controlling a current value applied to the load by the output from the comparator; and
a current detecting means generating the current feed-back signal by detecting the load current.
According to a second aspect of the present invention, there is provided an on-board current control device, wherein a volatile storage, memorizing the current adjusting information, is formed in the processing unit.
According to a third aspect of the present invention, there is provided an on-board current control device, wherein a nonvolatile storage, to which the current adjusting information is written, is formed in the processing unit.
According to a fourth aspect of the present invention, there is provided an on-board current control device, wherein a load subjected to the current control is an electromagnetic powder clutch.
According to a fifth aspect of the present invention, there is provided an on-board current control device, wherein a load subjected to the current control is an electromagnetic valve controlling an oil pressure.